gybbrellin and its role in plant
•
24 gostaram•24,034 visualizações
Gibberellins (GAs) are a class of plant hormones that affect several important processes such as seed germination, stem elongation, and flowering. Over 100 GAs have been identified in plants and fungi. GAs are synthesized through the mevalonic acid pathway and non-mevalonic acid pathway. Their biosynthesis involves multiple oxidation and hydroxylation steps. GA signaling involves perception by receptors, signal transduction through second messengers, and regulation of gene expression by transcription factors such as GAMyb. Mutations in GA biosynthesis, signaling, and response genes have helped elucidate the complex GA pathways and gene networks.
Recomendados
Mais conteúdo relacionado
Mais procurados
Mais procurados (20)
Semelhante a gybbrellin and its role in plant
Semelhante a gybbrellin and its role in plant (20)
Mais de Deepak Yadav
Mais de Deepak Yadav (18)
Último
Último (20)
gybbrellin and its role in plant
- 4. a class of plant hormones affect several important plant processes eg., seed germination stem elongation flowering male sterility Gibberellins (GAs)
- 6. Gibberellins 1926 Japanese scientist Gibberella fujikuroi gibberellin A (terpenoid cpd) 1954, 1955 US and UK scientists 1958 GA1 in higher plant GAx 1987 synthesis/metabolism
- 7. Gibberellins 1991 84 GAs 1995 89 GAs 64 plants, 12 fungi 13 both 1996 more than 100 / 136 1997 genes being cloned
- 8. Gibberellic acid (GA3) End metabolic product in fungi Plant GA20 GA5 GA3 Commercial High activity Slow degradation Similar to GA1 additional double bond
- 9. Gibberellins GA4 GA7 nonpolar, slowly diffuse GA9 GA12 precursor GA29 GA34 deactivated form Different tissues Different forms of GA
- 11. growing, differentiated tissues young, developing, expanding leaves developing seeds/fruit Gibberellins
- 12. elongated internode/petiole shoot/stem apex root cap/tip xylem sap Gibberellins
- 13. Synthesis and Metabolism Mevalonic acid pathway in cytosol Non mevalonic acid pathway in plastid
- 16. In higher plants from GA12 aldehyde Early 13-hydroxylation pathway (GA1) Non 13-hydroxylation pathway (GA4) with GA20oxidase genes: pathway shifted GA4 increased / GA1 decreased
- 17. GA12 aldehyde: precursor of GA derivatives by oxidation (C20) and hydroxylation (C13 C3 C2)
- 18. Vegetative tissue: conserved synthetic pathway 13-OH pathway to GA20 (C19-GA) then 3β-OH to GA1 except: arabidopsis and cucumber non 13-OH pathway to GA4 Reproductive tissue/seed: various pathways different forms of GA
- 20. From mevalonic acid (6C) GGPP (20C-linear cpd) ent kaurene (1st specific cpd) GA12 aldehyde (first GA) GAx
- 23. Isoprene (5C) as basic unit ent-Gibberellane skeleton tetracyclic diterpenoid cpd Gibberellins
- 24. 2 main types: C20-GA and C19-GA GA derivatives by modification of 4 rings * C20 oxidation: CH3 CH2OH CHO COOH * Hydroxylation at C2 C3 and C13: number, position stoichiometry * Loss of C20 (C20 to C19 GA)
- 26. * 2β-OH: GA20 GA29 GA1 GA8 * C20 oxidation to COOH GA inactivation
- 27. * Conjugation by glucose Glycosylation: inactive, storage and transport Glucose via COOH: GA glycoside Glucose via OH: GA glycosyl ether GA inactivation
- 28. GA synthesis mutants Pea na mutant: dwarf ent-kaurene GA12 aldehyde Pea le mutant: dwarf exogenous GA1 tall exogenous GA20 no response cloned Le gene:3β hydroxylase GA20 GA1
- 29. Considering 2 loci na Le normal ent-kaurene Na le normal GA20 Grafting 1. na Le scion Na le stock tall 2. Na le scion Na Le stock dwarf Conclusion?
- 30. Unlike auxin (acidification) Increase wall extensibility Decrease minimum force for wall extension GA mechanism in elongation
- 31. By (may) decrease Ca concentration in the wall increase Ca uptake into the cell reduce crosslinking of lignin-related cpd (via peroxidase) GA mechanism in elongation
- 32. GA mechanism in germination Activate transcription of α amylase gene In scutellum and aleurone
- 33. GA detection and assay Bioassay Easy but not specific Fractionation Plant response Lettuce hypocotyls elongation Microdrop/dwarf rice α amylase production
- 34. GC-MS Solvent extraction Chromatography (polarity) GC (boiling point) MS (mass) Identification and quantification High sensitivity and more specific
- 35. Inhibit ent-kaurene synthesis AMO1618 Cycocel Inhibit ent-kaurene oxidation Paclobutrazol Uniconazol Ancymidol Tetcyclasis Inhibit later steps by dioxygenases Bx-1112 LAB1988999 GA inhibitors
- 36. Hormone Responses Perception: receptor Signal transduction: second messenger (cAMP, cGMP) G protein Ca-Calmodulin enzyme transcription factor
- 37. At last step Gene expression Specific region in promoter cis element DNA-binding protein transcription factor
- 38. Exogenous GA / GA inhibitor GA mutant Gene identification / Gene cloning Gene expression / Transformation GA studies
- 39. Enzyme: gene product of multigene family Each gene with specific pattern of expression AtGA20ox1: shoot growth AtGA20ox2: inflorescence development AtGA20ox3: early seedling development GA synthesis
- 40. Genes controlled by GA, light and daylength GA: inhibit transcription of GA20oxidase (GA19 to GA20) inhibit 3β hydroxylase promote 2β hydroxylase At later steps of synthetic pathway
- 41. Light: promote conversion of GA1 to inactive GA8 reducing shoot elongation Negative feedback: reduce production of active GA20 and GA1Daylength (LD): floral initiation activates GA20oxidase activity GA53 to GA44 GA19 to GA20
- 42. Lettuce: Lactuca sativa seed germination Red light: activates LsGA3ox1 expression GA1 increase Far-red light: inhibits LsGA3ox1 Auxin: promote GA1 production inhibit deactivation steps to GA29 and GA8 Pea, Pisum sativum In de-etiolated pea seedling, exposed to red, blue, far red, all reduce GA1 level
- 43. Arabidopsis: seed germination assay 5 complementation groups (56 lines) ga1 ga2 ga3 ga4 and ga5 all recessive, dwarf, and male sterile ga1 and ga2 reversed by ent-kaurene ga3 reversed by ent-kaurenal GA synthetic mutants
- 44. GA1 kaurene synthase (ent-CDP synthase) GA3 Cyt P450-dependent monooxygenase GA4 3β hydroxylase GA5 GA20oxidase Genes
- 45. Pea (sln) decrease 2β hydroxylase activity increase active GA tall plant with light green leaves
- 46. Signal transduction mutants Stature mutants Decreased response to GA Increased response to GA
- 47. Dwarf Complete phenocopy of GA-deficient mutants No response to exogenous GA Decreased signaling mutants
- 48. Partially / fully dominant Arabidopsis gai Maize D8 D9 Wheat Rht1 Rht2 Rht3 Negative regulators Decreased signaling mutants
- 49. Dwarf Higher level of active GA and GA20oxidase Semidominant Arabidopsis gai mutant
- 50. gai1-1 51 bp inframe deletion loss of 17 amino acid constitutive repressor Arabidopsis gai mutant
- 51. Arabidopsis gai mutant intragenic suppressor of gai loss of function allele WT phenotype
- 52. Maize D8 mutant Dwarf Higher level of active GA 6 dominant alleles with different severity
- 53. 8 dominant alleles with different severity Dwarf: prevent lodging Wheat + N fertilizer: increase yield increase height Norin10: dwarf line 2 mutated loci: Rht1 or Rht-B1b (chrs 4B) Rht2 or Rht-D1b (chrs 4D) Wheat Rht mutant
- 54. All genes cloned: deduced amino acid sequence GAI / Rht / d8 homologs Conserved domains I and II in N terminal gai mutant: deletion in domain I D8 / Rht: mutation in domain I and/or II *N terminal essential for GA response*
- 55. Similar to WT + GA Tall by elongated internodes Arabidopsis spy rga Barley sln spy Rice slr Tomato pro Pea la crys Recessive / Negative regulators Increased signal transduction mutants
- 56. Arabidopsis rga Identified by suppression analysis of ga1-3 New mutant: taller ga1-3 < ga1-3* < WT new locus: repressor of ga1-3 (rga) Increased signal transduction mutants
- 57. rga: recessive (deletion mutation) increase stem elongation reverse ga1-3 delayed flowering time no effect on GA biosynthesis RGA: negative regulator Gene: 82% homology to GAI especially in N region Increased signal transduction mutants
- 58. Original gai mutant: gain of function Loss of function allele of GAI ? Phenotype: normal Increase paclobutrazol resistance Low GA = normal height
- 59. At least two components in Arabidopsis GA signaling pathway GAI and RGA homopolymeric Serine / Threonine residue leucine heptad for protein-protein interaction putative nuclear localizing signal
- 60. slender mutant recessive long internodes and narrow leaves male sterile increase α-amylase w/o GA low endogenous GA resistant to GA synthesis inhibitors Barley sln
- 61. negative regulator sln x dwarf mutant = sln phenotype SLN = GAI/RGA homolog Dominant allele of SLN mutant Mutation in N terminal Dwarf barley
- 62. slender rice recessive phenocopy of barley sln 1 bp deletion in NLS domain (nuclear localization signal ) Rice slr
- 63. frame shift mutation stop codon truncated protein SLR gene = SLN homolog Modified SLR: 17 aa deletion in DELLA domain Transformation: dwarf rice Rice slr
- 64. GA signal component Dicot / Monocot GAI RGA Rht d8 SLN SLR Putative transcription repressor
- 65. spindly mutant, recessive paclobutrazol-resistant long hypocotyls light green leaves early flowering spy ga1-2 = spy phenotypes spy gai = spy phenotypes Arabidopsis spy
- 66. SPY gene product: O-GlcNAc transferase Signaling molecule Involved in protein-protein interaction Negative regulator Arabidopsis spy
- 67. Before responses Expression of GA-regulated genes: Protein-DNA interaction Transcription factor cis elements
- 68. Barley: HvGAMyb Bind specific sequence in promoter of α-amylase gene Increase gene expression Overexpression of HvGAMyb gene = GA treatment Transcription factor: GAMyb
- 69. Arabidopsis: GAMyb-like genes AtMyb33 AtMyb65 AtMyb101 Functional homologs of barley GAMyb Transform barley aleurone with AtMyb33 Activate α-amylase production
- 70. Arabidopsis: facultative LD plants Transfer plants from SD to LD 11x increase of GA1 3x increase of GA4 increase AtMyb33 expression in shoot apex shoot apex transition to flowering
- 71. Potential target for AtMyb LFY promoter LEAFY: meristem-identity gene Evidence AtMyb binding to a specific 8-bp sequence in LFY promoter
- 72. cis elements specific regions in promoter transcription factor binding site identified by deletion or site specific mutagenesis: gene expression after promoter modification
- 73. - amylase box: TATCCAT - GARE: TAACAA/GA - Pyrimidine box: C/TCTTTTAC/T Conserved sequences among GA-regulated genes
- 74. GA and α-amylase production Perception at membrane receptors Increase intracellular Ca Decrease intracellular pH Increase [CaM] Increase cGMP Increase GAMyb transcription Increase α-amylase activity Some protein phosphorylation